Effects of Drying Temperature for Cryptomeria japonica on the Permeability of Wood Preservative. II: The Permeability of Dried, Split Log Pieces

Abstract

e Poor impregnation of sapwood from Cryptomeria japonica kiln-dried logs is a problem for preservative treatment in Japan. The permeability of copper azole (CuAz) into sapwood was reported to decrease with an increase in the drying temperature of logs, due in part to the presence of bordered pits. However, damaged and aspirated bordered pits appeared abundantly at 100 °C and 120 °C, although the difference in permeability was very little. To investigate this phenomenon, two types of smaller split log pieces, one containing both heartwood and sapwood, and the other containing sapwood without heartwood, were dried at 20 °C to 120 °C to test higher drying conditions. Results were similar to those of the dried logs. However, the impregnation and penetration at 80 °C were the lowest, and those at 100 °C and 120 °C were greater than the dried logs. Additionally, the number of damaged bordered pits on dried, split samples was generally higher than that of dried logs, as observed with scanning electron microscopy. Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1 Hakozaki Higashiku Fukuoka, 812-8581, Japan; c: Division of Forest Environment Sciences, Faculty of Agriculture, Kyushu University, 394 Tsubakuro Sasaguri Fukuoka, 812-2415, Japan; d: Department of Wood Processing and e: Department of Research Planning and Coordination, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687 Japan; * Corresponding author: h-sakagami@agr.kyushu-u.ac.jp Keywords INTRODUCTIONCryptomeria japonica D. Don is the most popular domestic commercial wood in Japan, and its effective utilization is important. Recently, small logs and sawn timbers have been used for civil engineering (Kamiya 2003;Kubojima et al. 2012;Noda et al. 2014). Most woods destined for these uses are treated with wood preservative. However, it is difficult to impregnate the timber evenly with preservative due to non-uniform permeability by some factors. (Erickson 1970;Flynn 1995). Problems with sapwood permeability for C. japonica kiln-dried logs have gained special attention due to deterioration of durability in Japan. The preservative penetration of air-dried logs is significantly better than that of the kiln-dried logs (Momohara et al. 2009). Although the details are not specified, the cause is likely the different log drying conditions. Fluid flow in softwoods, both sapwood and heartwood, is generally related to the shape, size, and conditions of pits in tracheids. According to Fujii et al. (1997), air permeability has an obvious negative correlation with the pit aspiration ratio in samples collected from sapwood, transition zone between sapwood and heartwood, and heartwood.PEER-REVIEWED ARTICLE bioresources.com Sakagami et al. (2016). "Permeability of split log," BioResources 11(3), 6896-6908. 6897Fluid flow is clearly influenced by drying conditions. Studies on the relationship between fluid flow and drying conditions have contradictory results after high temperature drying, reporting enhanced perme...

Exploratory studies on effects of growth location and conditioning on treatability and permeability of southern pine lumber

“…Gas permeability of subalpine fir (Abies lasiocarpa) lumber experienced no significant change after 4 hr of steaming in either the green condition or at the fiber saturation point (Cai and Oliveira 2007). Bordered pit damage and aspiration were more prevalent in Cryptomeria japonica sapwood lumber dried at 100ºC to 120ºC than similar lumber dried at far lower temperatures, but permeability measurements were similar (Sakagami et al 2016). Anecdotally, some southern pine kiln operators have found improved treatment results when lowering initial kiln-drying temperature by 5ºC to 10ºC or limiting venting to achieve higher wet-bulb temperatures early in the kiln-drying process to produce more rapid heating of the wet wood while delaying early rapid drying (Winandy et al 2001, Donn Keefe, Personal communication, 2001.…”